Generally, a muffler is a device for reducing noise of exhaust gas and is applied to an exhaust system of a vehicle, an industrial machine, or the like.
A muffler generally includes a body having a hollow inner space, a partitioning wall which partitions the inner space of the body and has a plurality of through holes, an inlet pipe which introduces exhaust gas into the body, and an outlet pipe which discharges the exhaust gas in the body. In such a muffler, exhaust gas is introduced via the inlet pipe and passes through the through holes of the partitioning wall and is finally discharged via the outlet pipe. However, the size and the position of the through hole are fixed, so flow of exhaust gas cannot be suitably regulated depending on engine RPM.
In order to solve this problem, a muffler disclosed in Korean Patent No. 0325741, as shown in FIG. 11, includes a shell 3 forming a body, a plurality of partitioning walls 4a, 4b and 4c partitioning an inner space of the shell 3 and having a plurality of porous pipes 5a, 5b and 5c, an inlet pipe 1 which introduces exhaust gas into the body, a plurality of outlet pipes 2a and 2b which discharges exhaust gas, an opening/closing valve 6 which is disposed at a frontal end of one outlet pipe 2b of the outlet pipes, a compressed air source 8 which is an actuator for driving the opening/closing valve 6, and an ECU 7 which operates the compressed air source 8 in response to an engine RPM to regulate the opening/closing valve. Accordingly, flow of exhaust gas is regulated in response to an engine RPM so that noise of exhaust gas and back pressure can be reduced.
However, since in such a conventional muffler the actuator 8 and the ECU 7 are separately provided and the opening/closing valve 6 is forcibly operated, the muffler is complicated due to these elements and design freedom is limited, and manufacturing cost is also increased.